Exemplary embodiments of the invention relate to a method for operating a distance and speed regulating function of a vehicle and a driver assistance system for carrying out such a method and a vehicle having such a driver assistance system.
A generic method for operating a distance and speed regulating function of a vehicle is known from German patent document DE 10 2011 117 431 A1 in which the level of attentiveness of a driver of the vehicle is detected and in which, depending on the level of attentiveness detected, measures for increasing the driving safety are introduced, wherein these measures comprise a change of a nominal distance or a nominal speed of the distance and speed regulating function.
A method for operating a vehicle is known from German patent document DE 102010049081 A1 in which it is ascertained whether the driver of the vehicle is distracted because of an actuation of operating elements of the vehicle's system, for example an information and entertainment system, an air conditioning system, a mirror adjustment device, a seat adjustment device, a navigation system, a driver assistance system or a telephone system. If this is the case, a nominal distance of a distance regulating function of the vehicle is increased which leads to an increase in driving safety.
Exemplary embodiments of the invention are directed to a method of the type mentioned above and a driver assistance system and a vehicle, in which the operating mode of the distance and speed regulating function is improved.
In the method according to the invention for operating a distance and speed regulating function of a vehicle, hereinafter called the ego-vehicle, at least one measure increasing driving safety is introduced when the predetermined trigger criteria for introducing these measures are fulfilled. The predetermined trigger criteria here comprise the determination of low driver attentiveness of the driver of the ego-vehicle, and the fulfilment of at least one of the following additional conditions:                a) the ego-vehicle is approaching a location that is critical in terms of the route, for example a curve, an inclined section, a lane constriction, an entry slip road or an exit slip road, or the ego-vehicle is already at such a location,        b) the ego-vehicle is approaching a location with traffic disruptions, for example a building site or a traffic jam, or the ego-vehicle is already at such a location,        c) the ego-vehicle is approaching a location with visibility impairments, for example a tunnel entry or tunnel exit, or the ego-vehicle is already at such a location,        d) the ego-vehicle is accelerated by the distance and speed regulating function, for example because of a road becoming clearer after a slow vehicle ahead has turned off,        e) the ego-vehicle is at a location at which there is an anomaly of the traffic flow, which is the case, for example, when there is a higher vehicle density in adjacent lanes than in the lane of the ego-vehicle, and/or when a speed decrease relative to the speed of the ego-vehicle is registered in adjacent overtaking lanes and/or when a speed increase relative to the speed of the ego-vehicle is registered in adjacent non-overtaking lanes. Here, overtaking lanes are lanes that are to be used for overtaking procedures, and non-overtaking lanes are lanes that are not to be used for overtaking procedures.        
This means that the condition for the introduction and preferably also for the implementation of the at least one measure increasing driving safety is that the driver of the ego-vehicle is inattentive and that one or more of the conditions a) to e) is fulfilled. Advantageously, the at least one measure increasing driving safety is terminated or ended after its introduction when it is determined that the driver is attentive again, or when the trigger criteria for the introduction of the at least one measure increasing driving safety are no longer fulfilled.
In an advantageous embodiment of the method, the at least one measure increasing driving safety comprises at least one of the following actions:                the emission of a warning to the driver of the ego-vehicle in order to request the driver to turn his/her attention to the traffic,        the increase of a nominal distance of the distance regulating function, in particular up to a maximum distance that can be predetermined,        the limitation of a nominal speed of the speed regulating function, in particular to a value below a maximum speed that can be predetermined, which is preferably predetermined depending on a traffic flow in the vehicle surrounding area of the ego-vehicle. Here, traffic flow is to be understood as the average number of vehicles that pass a route section per time unit.        
With the ego-vehicle, the method according to the invention is advantageously used during an automatic or highly automated driving operation.
The driver assistance system for a vehicle is set up according to the invention for carrying out the method according to the invention, and it is a component of a vehicle driving automatically or in a highly automated manner.